1. Technical Field
The present invention relates to a vertical stand-up package made from a modified vertical form, fill, and seal packaging machine, and the apparatus and method for making same, that provides for a single piece construction of a vertical stand-up package. In particular, the invention reduces the pleating that can occur when filling a vertical stand-up package with minimal cost increase and minimal modification.
2. Description of Related Art
Vertical form, fill, and seal packaging machines are commonly used in the snack food industry for forming, filling, and sealing bags of chips and other like products. One such packaging machine is seen diagrammatically in FIG. 1. This drawing is simplified and does not show the cabinet and support structures that typically surround a machine, but it demonstrates the working of the machine well. Packaging film 110 is taken from a roll 112 of film and passed through tensioners 114 that keep it taut. The film then passes over a former 116, which directs the film into a vertical tube around a product delivery cylinder 118. As the tube is pulled downward by drive belts 120 the vertical tube of film is sealed along its length by a vertical sealer 122, forming a back seal 124. The machine then applies a pair of heat sealing jaws 126 against the tube to form a transverse seal. This transverse seal acts as the top seal 133 on the bag 130 below the sealing jaws 126 and the bottom end seal 131 on the bag 132 being formed above the jaws 126. After the transverse seal has been formed, a cut is made across the sealed area to separate the finished bag 130 below the seal from the partially completed bag 132 above the seal. The tube is then pushed downward to draw out another package length. Before the sealing jaws 126 form each transverse seal the product to be packaged is sent through the product delivery cylinder 118 and is held within the tube above the bottom end seal 131. The material that is fed into the form, fill and seal machine is typically a packaging film such as polypropylene, polyester, paper, polyolefin extrusions, adhesive laminates, and other such materials, or from layered combinations of the above. For many food products, where flavor retention is important, a metalized layer will form the inner most layer.
One modification to a vertical form, fill, and seal packaging machine is disclosed in U.S. Pat. No. 6,722,106 (“the '106 Patent”), which is assigned to the same assignee as the present invention. The '106 Patent discloses a method for making a free standing package called a vertical stand up pouch. The modification uses two forming plates 104 and a tension bar 102 to hold the packaging film tube in tension from inside the tube. Tension is applied on the outside of the film and in the opposite direction of the tension provided by the forming plates 104 by a fixed or stationary tucker mechanism 106 positioned between the forming plates 104. The tucker bar 106 provides a crease or fold in the tube of the packaging film between the two forming plates 104. The crease is formed prior to formation of the transverse seal by the seal jaws 126. Consequently, once the transverse seal is formed, the crease becomes an integral feature of one side of the package. The vertical form and fill machine thereafter operates basically as previously described in the prior art, with the sealing jaws 126 forming a lower transverse seal 131, product being introduced through the forming tube 118 into the sealed tube of packaging film which now has a crease on one side, and the upper transverse seal being formed, thereby completing the package. An example of the vertical stand up package formed shown in FIGS. 2a and 2b, which show the outside layer of packaging film 116 with the graphics oriented 90 degrees clockwise from graphics orientation normally present on a pillow pouch formed by a standard prior art vertical form, fill and seal machine. As shown in FIGS. 2a and 2b the transverse seals 131, 133 of the vertical stand up package are oriented vertically once the bag stands up on one end as shown in FIG. 2b. 
FIG. 2a shows the crease 176 that was formed by the tucker bar 106 and forming plates 104 to create a gusset 180 base bounded by an edge that permits the package to stand upright. Various modifications of the vertical stand up pouch, methods for making the pouch, and apparatuses for making the pouch are disclosed in U.S. Pat. Nos. 6,729,109 and 6,679,034.
Referring back to FIG. 1, after the transverse seal is formed by the pair of sealing jaws 126, an open-ended tube is created. The open-ended tube is pulled downward by drive belts 120, product is dropped into the open-ended tube and the bag is formed upon completion of the second end seal 133. Unfortunately, the weight of the product dropping into the open-ended tube can apply pressure to the gusset portion 180 of the open-ended tube and can cause the flexible film tube to twist or rotate below the fill tube about the fill tube axis. If the flexible film tube is twisted when the sealing jaws 126 are brought together to make the end seals 131 133, the gusset 180 can be sealed at the ends at the location indicated by numeral 141 and 143, thus forming a pleat 151 153. Pleats 151 153 are undesirable for several reasons.
FIG. 2c is a perspective view of a vertical stand up package having pleats. There are several problems associated with pleats. First, as shown by the Figure, a pleat can cause edge erosion. Edge erosion can inhibit the ability of the vertical stand up package to stand upon the gusset 180. Second, bags having pleats can have higher propensity to produce a non-hermetic seal and result in reduced shelf life. This can be especially true if pleats are in unpredictable or inconsistent locations. Third, pleats can interfere with easy opening features of a bag. For example, to provide an easy opening feature, a cut out 155 156 can be provided on the end seals 131 133 in communication with a score line 152 placed on the container by methods known in the art. Normally, upon tearing in the vicinity of the cut out 155 156, the film will continue to tear along the score line 152. The cut out 156, however, can be sealed by a pleat 141, preventing initiation of a tear along the score line 152. Consequently, a need exists for a vertical stand-up package having no pleats. The method and apparatus should be economical and should permit modification to existing vertical form, fill, and seal machines. In addition, the method and apparatus should minimize the breakage of frangible product within the package.